The invention relates to a reaction vessel suitable for carrying out an exothermic reaction of a liquid reactant with a gaseous reactant to form a gaseous reaction product at elevated temperature and elevated pressure, wherein the residence time of the gaseous reactant in the reaction vessel is increased by non-pressure-bearing internals.
Such a reaction vessel is preferably used for preparing hydrogen sulphide from sulphur and hydrogen. The reaction vessel contains internals which increase the residence time of the hydrogen in the liquid sulphur, with the gas being collected in parts of these internals and subsequently being dispersed again in the liquid sulphur.
Hydrogen sulphide in particular is an industrially important intermediate, for example for the synthesis of methyl mercaptan, dimethyl sulphide, dimethyl disulphide, sulphonic acids, dimethyl sulphoxide, dimethyl sulphone and for numerous sulphiding reactions. It is nowadays obtained predominantly from the refining of petroleum and natural gas and also by reaction of sulphur and hydrogen.
The synthesis of hydrogen sulphide from the elements hydrogen and sulphur is usually carried out by introduction of hydrogen into the liquid sulphur and subsequent reaction in the gas phase in a downstream reaction space. Both catalysed and uncatalysed processes are known here. The synthesis of hydrogen sulphide is usually carried out in the gas phase at temperatures of from 300 to 600° C. and pressures of from 1 to 30 bar. The industrial production of hydrogen sulphide from the elements proceeds, according to Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH, 2002, at temperatures of 450° C. and a pressure of 7 bar.
GB 1193040 describes the uncatalysed synthesis of hydrogen sulphide at relatively high temperatures of from 400 to 600° C. and pressures of from 4 to 15 bar. It is stated that the temperature required is determined by the pressure at which the synthesis is to be carried out. According to that text, about 500° C. is required at a pressure of 9 bar.
An important factor in the preparation of hydrogen sulphide from sulphur and hydrogen is, in particular, the temperature conditions. High temperatures are necessary to achieve an equilibrium state in which a molar ratio of hydrogen:sulphur of about 1:1 is established in the gas phase. Only this makes the synthesis of pure hydrogen sulphide possible. As the pressure increases, the temperature has to be increased greatly corresponding to the vapour pressure curve of sulphur in order to achieve the desired molar ratio of 1:1 in the gas phase. Even small differences in pressure of, for example, 1 bar or less are of great importance.
CSSR 190792 describes a process variant for the preparation of hydrogen sulphide, in which high reaction temperatures are avoided by means of a comparatively complicated arrangement of a plurality of reactors in series. High temperatures are specifically avoided there because of corrosion problems. CSSR 190793 reports severe corrosion of the plant at temperatures of 400° C. upwards.
U.S. Pat. No. 4,094,961, too, reports severe corrosion at temperatures of from 440 to 540° C. in the synthesis of hydrogen sulphide. The synthesis is therefore carried out there at temperatures below 440° C.
The article by B. Glaser, M. Schütze, F. Vollhardt on “Auswertung von Daten zum H2S-Angriff auf Stähle bei verschiedenen Temperaturen und Konzentrationen”, Werkstoffe und Korrosion 42, 374-376, 1991, states that in the case of plants in which corrosive attack by H2S is to be feared at elevated temperatures, this is significantly hindering the further development of such plants. In particular, a move to higher temperatures and thus an improvement in the economics of the corresponding processes has hitherto been ruled out since in this case tremendous corrosion damage and thus downtime of the plants occurs even after short times. The temperature and the H2S concentration are named as main factors influencing the corrosion.
Depending on the further use of hydrogen sulphide, it can be highly advantageous to provide the hydrogen sulphide at relatively high pressure and not have to compress it separately.
The economics of the process requires very low capital and operating costs. Here, major cost factors are, in particular, the outlay for apparatuses and machinery and also the energy consumption for the synthesis and treatment of the starting gas mixture. For example, operation of compressors and of heating and cooling circuits consumes a large amount of electric power.